1. Field of the Invention
The present invention relates to an ultrasonic probe and a piezoelectric transducer that generate ultrasonic waves with transmission intensity weighted.
2. Description of the Related Art
There is a ultrasonic probe which has a plurality of piezoelectric transducers arranged in an array direction. In the linear array ultrasonic probe, when a drive signal is applied to the respective piezoelectric transducers, side lobes in acoustic fields in a lens direction cause problems or the acoustic fields in the lens direction are made non-uniform. Therefore, as a technique to reduce side lobes or to make acoustic fields uniform, weighting the ultrasonic waves in the lens direction is conducted to change the intensity distribution of ultrasonic waves transmitted and received to/from a piezoelectric transducer.
As a technique for weighting in this way, there is a method for achieving desired weighting on the ultrasonic wave intensity in the lens direction by disposing the piezoelectric transducers and grooves for dividing the piezoelectric transducers alternately at predetermined intervals (for example, see Jpn. Pat. Appln. KOKAI Publication No. 2003-9288).
As another technique for weighting, there is a method of forming grooves in the lens direction which are arranged on the top surface or bottom surface or both, of piezoelectric transducers at the depth and intervals in accordance with weighting and at the same time which do not divide the piezoelectric transducers (for example, see Jpn. Pat. Appln. KOKAI Publication No. 2005-328507).
However, the technique stipulated in Jpn. Pat. Appln. KOKAI Publication No. 2003-9288 deals with a structure to completely divide the piezoelectric transducer by grooves (so-called composite structure), and therefore, it is difficult to manufacture an ultrasonic probe. In addition, electrodes must be formed on the resin material filled in grooves, but adhesion of electrodes to the resin material is low and the low reliability of an ultrasonic probe results.
In addition, in the technique stipulated in Jpn. Pat. Appln. KOKAI Publication No. 2005-328507, the weighted intensity depends also on the groove depth. That is, in order to obtain still intensified weighting, still deeper grooves are required. When deep grooves are formed, mechanical strength of piezoelectric transducers is lowered. In addition, in this technique, a plurality of piezoelectric transducer pieces are formed by a plurality of grooves. In this kind of structure, it is important to definitely connect an electrode to each one of the piezoelectric transducer pieces. However, it is difficult to connect electrodes to a plurality of piezoelectric transducer pieces with high reliability by pressure-bonding piezoelectric transducer pieces having high rigidity to acoustic matching layers (or flexible PC boards).